Concentrating ores



Patented Dec. 23, 1941 UNITED-STATES PATENT OFFICE W 5 Anderson W. .Ralston' and William 0. Pool, Chi-' cago, Ill., assignors to Armour and Company, Chicago, 11]., a corporation of lllinols I No Drawing.

Application December 17, 1936, Serial No. 116,422

11 Claims. (cirzoe ise) This invention relates to the froth separation of metalliferousores.

The prior artis repletejwlth various processes.

of ,concentratingmetalliferous ores' by the use of frothing agents, collecting agents, and the like. All ofv these methods involve the preparae tion of an aqueous pulp of the ore, the addition" to the pulp of 'frothing. and collecting agents, and the aeration of the mixture whereby* th e metalliferous values in the ore :are icaused-to' amines having 10 .or more carbon atoms in the alkyl radical. The lowest member of this series is de'cylamine and theseriesincreases to octadecylamine havingkltgcarbonatoms in the alkyl radical. We have discovered that the primary q'alkyl amines are very efiicient frothing agents. The secondary alkyl amines, such as di-octadecylamine, are insoluble in water and are excellent collecting; agents.

collect as a froth which can. befie dily sepa atedfrom the body of liquid. The gangue" remains in the aqueous pulp and in this manner a s epa ration between gangue and .metalliferous. con,

stituents is effected. r One of the earliest known frothing agents ,was

oleic acid. Following the discovery of this genv I In one modification of our invention 'weutilize ,mixtures of aliphatic amines prepared byreducing an aliphatic nitrile with hydrogen. For example, heptadecilonitrile scan be reduced with hydrogen gas in the vapor s tate to'give reduction products consisting of a eral method'of concentrating ores many different reagents have been used for obtaining various 3 specific results during the frothing process. For

examplait is considered necessary that the metalliferous ore should be rendered non-wettable without affecting the gangue. In theory the 7 various oily materials added in very small quantities to the ore pulp are intended to: coat the metalliferous ore, thus rendering it noln-wettable by water. This action should be specific so that "mixture-of primary, secondary, and tertiary octade'cylamines, together with unreduced heptadecilomtrile; This mixture can be prepared at little expense and, when added to a metalliferous ;ore pulp acts as an excellent froth flotation triles to the amino compounds can be effected the gangue particles are not coated by the oil.

Froth flotation thus involves two factors.

that its interfacial tension towards water is changed without affecting the gangue. a frothing agent must be present to insure the formation of relatively stable bubbles during the aeration. When these two factors are present, the admixture of airwith the pulp results in the formation of stable bubbles which adhere to the surface-modified metalliferous ore causing it to rise as a froth. Further developments in the art have led to theuse of so-called depressing substanceswhichhelp to depress any tendency for the siliceous gangue to float.

As stated, the art has hitherto made use of two substances in froth flotation, one of which is customarily referred to in the art as a collector substance, and the other as a frothing substance. For example, oleic acid, fuel oil, and other hydrocarbon oils have been used as collectors. Common soap is one well-known frothing agent and many other substances, such as ketones, have been proposed. 7

We have now discovered a class of chemical compounds which can be prepared at little expense and which function as frothing agents in froth flotation, and which also function as col- Second,

First, so modifying the surface of the metalliferous ore lecting agents. These compounds are alkyl 55 with hydrogen gas as stated, or the nitriles can be reduced with sodium and an alcohol as described, for example, in the Harwood application, Serial Number 104,708, filed October 8, 1936, now Patent No. 2,122,644.

In addition to the use of primary alkyl amines,

or admixtures thereof, with secondary amines, tertiary amines, and nitriles, we can, of course, add collecting agents such as oleic acid, fuel oil, tarry hydrocarbon oils and similar well-known collecting agents.

Before describing our invention with specific reference to the flotation of particular ores, we wish to point out at this time that our flotation reagents and processes can be used with any of the usual metalliferous ores hitherto subjected to froth flotation. Thus for example, we can float the various oxide ores such as magnetite, corundum, ilmenite, rutile, chromite, cuprite,

' zincite, franklinite, pyrolusite, and cassiterite.

Our invention is also applicable to the concentration of the various sulphide ores such as copper sulphide.

In the practise of our invention, we follow procedures customarily used for the froth flotation of these ores. In common with prior practise, we first grind the ore to about 40 to 100 mesh. It is better to avoid the presence of large quantities of slime, namely those particles having mesh finer than 100.

The mixture of ground are and water in the usual proportions is then admixed with small quantities, usually not more than about 5 pounds to a ton of ore of one or more of our primary aikyl amines, or admixtures thereof with secondary and tertiary amines. The final mixture is then subjected to common devices, such as the Callow cell customarily used in this art. Thus, for example, cassiterite ground in a ball mill to the mesh stated is pulped in water to which about one to five pounds per ton of ore of octadecylamine is added. We also find it advantageous to add about one pound per ton of ore of oleic acid or coal tar to act as a collecting agent. This mixture is then frothed and from a pulp originally containing about 25% of tin, we obtained a froth assaying about 60% of tin.

Similar results are obtained when oxidic ores of copper are used and about the same proportions are observed. Even better segregation of the metalliferous ore is observed when sulphide ores are subjected to froth flotation in the presence of our primary alkyl amines.

Instead of using substantially pure octadecylamine, we can use as stated, admixtures of primary and secondary octadecylamines which may in addition contain small quantities of tertiary amines and alkyl nitriles.

Thus, for example, to a pulp of a sulphide ore, such as copper sulphide, we add about five pounds per ton of ore of a mixture of primary and secondary octadecylamines in which the primary amine amounts to about 70% of the total. When using this mixture, we need not add an oil, such as oleic acid or furnace oil, to act as a collector because as stated, we have discovered that the secondary and tertiary amines and probably also the nitriles, function as collecting agents.

Generally our amine mixtures will contain a greater proportion of primary alkyl amine, a somewhat lesser amount of secondary amine and still smaller amounts of tertiary amines and nitriles. One typical analysis of the product made by reducing heptadecilo nitrile with hydrogen is as follows. Primary octadecylamine 72%, dioctadecylamine 21%, tri-octadecylamine 4% and the rest heptadecilo nitrile.

Although we have in our specific examples referred to octadecylamines, we wish it understood that other amines or amine mixtures in which the alkyl radicals have at least carbon atoms are effective. Thus the amine can be decyl, dodecyl, hexadecyl and octadecyl, or mixtures thereof of two or more of these amines. For reasons of economy, and also for somewhat better action with less flotation reagent, we find it more advantageous to use those amine mixtures in which the alkyl radicals of the amine contain 18 carbon atoms. This is because these amines can be prepared readily from stearic acid which is relatively cheap. The stearic acid is converted to heptadecilo nitrile and the heptadecilo nitrile then subjected to reduction as stated. We do not intend to be limited to the use of the saturated aikyl amines. One of the best flotation agents we have observed is octadecenylamine which can be prepared from oleic acid froth flotation in any of the by first converting the oleic acid to its corresponding nitrile and then reducing the nitrile under carefully controlled conditions to form an aliphatic amine in which the alkyl radical is unsaturated and contains the double bond found in oleic acid. However, the position of the double bonds in the unsaturated amine may be different from the position of the bonds in oleic acid. The precise position of these double bonds has not been determined, but we do know that the amines prepared from oieo nitrile are unsaturated.

Consequently, in the appended claims, we intend our alkyl amines to embrace both the saturated and unsaturated amines.

Our invention is to be distinguished from the use of amino compounds such as triethanolamine and oleates made therefrom. These amines are not unsubstituted alkyiamines as claimed in the appended claims.

Having thus described our invention, what we claim is:

1. In the froth separation of metalliferous ores, the step comprising effecting the froth separation in the presence of a straight chain unsaturated primary aliphatic amine having at least ten carbon atoms.

2. In the froth separation of metalliferous ores, the step comprising effecting the froth separation in the presence of octadecenylamine.

3. In the frotlr separation of metalliferous ores, the step comprising effecting the froth separation in the presence of a mixture of primary and secondary aliphatic amines having at least ten carbon atoms in the alkyl group thereof, the major portion of the mixture consisting of the primary amine, there being enough primary amine to act as a frother and enough secondary amine to act as a collector.

4. In the froth separation of metalliferous ores, the step comprising effecting the froth separation in the presence of a mixture of octadecylamine and dioctadecylamine, the major portion of the mixture consisting of octadecylamine, there being enough octadecylamine to act as a frother and enough dioctadecylamine to act as a collector.

5. The process as set forth in claim 3, wherein the ore is a sulfide ore.

6. The process 'as set forth in claim 3, wherein the ore is an oxide ore.

7. The process as in claim 3, wherein the pri- Rary amine constitutes about of said mix- 8. The process as in claim 3, wherein the primary amine constitutes about 72% of the mixture, and the secondary amine about 21%.

9. The process as in claim 3, wherein the primary amine constitutes about 72% of said mixture, the secondary amine about 21%, and the remainder being tertiary amines and nitriles.

10. The process as in claim 3 wherein the mixture also contains another collecting agent in addition to the secondary amine.

11. The process as in claim 3 wherein the mixture contains a hydrocarbon oil as collecting agent.

ANDERSON W. RAISTON. WILLIAM O. POOL. 

